FULL PRODUCT VERSION :
java version "1.6.0_05-ea"
Java(TM) SE Runtime Environment (build 1.6.0_05-ea-b04)
Java HotSpot(TM) Client VM (build 1.6.0_05-ea-b04, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Windows XP

A DESCRIPTION OF THE PROBLEM :
In Nimbus, if you try to set a different background color using setBackground(), it is ignored.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Add a JCheckBox to a frame and set its background color to anything other than the standard (for example, checkbox.setBackground(new java.awt.Color(255, 255, 153)). Under Nimbus, this new background color will not be used. The background color of the container of the checkbox will be used instead.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Having the checkbox displayed with the background color passed in setBackground().
ACTUAL -
The checkbox is displayed with the background color of its container.

REPRODUCIBILITY :
This bug can be reproduced always.